Nair and Adams, in the Journal of the American Chemical Society, Vol. 33, pp. 3518-3521 (1961), describe the preparation of certain tricyclic morpholinobenzimidazole compounds by the oxidative cyclization of ortho-anilinomorpholine compounds with peroxytrifluoroacetic acid. The reaction can be illustrated by the following equation. ##STR1## in which X represents hydrogen, chloro, methyl or nitro.
Fielden et al., Journal of the Chemical Society, No. 7, pages 696-701 (1973) report the preparation of 1,2-morpholinobenzimidazole N-oxide and its 5-nitro derivative by cyclization of the corresponding ortho-nitrophenylmorpholine compound.